Pneumatic percussive tool



E. W. STEVENS PNEUMATC PERCUSSIVE TOOL Filed May 25, 1925 Sqwff K Y May 24, 1927.

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Patented May 2d, 1922"?.

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EDWARD W. STEVNS., OF DETROIT, MICHIGAN, ASSGNO TO CHICAGO PNEUMATIC TOOL COMPANY, O1" NEW' YORK. N. `Y., CGRPQRATION 0F NEW JERSEY. i

PNEUMATIC -PVERCUSSVE TOOL,r

Application filed May 23, 192.5. ASerial No. 32,250.

This invention relates to fluid pressure percussive tools of the type utilizing a two diameterV piston providing two pressure areas for driving it in one direction and a single pressure `area for returning it.

One object of the invention is to provide a tool of the class vdescribed in which ,ex-

ternal projections are avoided thereby maky ing it compact and of relatively light weight. Another object is to provide atool having superior ruiming .characteristics Other objects will appear from the detailed descrip-` tion which follows. Y

In order to illustrate the invention a preferred embodiment thereof is shown in the accompanying drawings, in which:

Fig. 1 is a longitudinal sectional view;

Fig. 2 is a view similar to Fig. 1 showing the movable parts in a different position;`

The embodiment of the invention shown comprises a stopingdri ll having the cylinder 4l providing a piston chamber in which re-r ciprocates a hammer piston 5 arranged to deliver blows -upon a working tool or drill steel 6, supported in a front head or chuck 7, either directly or through an anvil block 8 which may be mounted in a guide member 9 interposed between cylinder l and chuck 7. The tool is provided at its rear end with a feed cylinder 10 within which is mounted for sliding movement a feed piston (not shown) actuated by motive fluid admitted through la restricted port 11 under control of a throttle valve 12 for moving the -drill bodily to its work. Thepiston chamber is differential in size having a larg-e bore l and a small bore 4b and the piston 5 corresponds theretocomprising a head 5L fitting the large bore l and a stemv5" fitting the small bore 1lb. Disposed in a counter-bore in the rear end of small bore l isa sleeve valve 13 defining a portion lof the small scribed. lWhile a singlev annular series of large inlet ports 13' may be provided, it is preferred to use two spaced annular series of small ports as shown in order to prevent the valve from being unduly weakened at this point. The anges 13b are symmetrically disposed onl valve 13 and grooves 13c arev symmetrically disposed upon flanges A13b in order to make the valve reversible. y

ln -tlie reciprocation of the piston ythe stem 5b passes v.within the valve 13 as -indicated in 1 thus cont-rolling the admission of motive fluid from live air chamber 14 through ports 13zt to the small bore of the piston chamber;- The stem .5b also controls a port 15 communicating with a passageA 15a n opening into the front end of the largev piston bore l? through a por-t 15b. A communicatingpassage 15c extends to the rear and communicates with a port 15d in rearward spaced relation with port 15, the port 15d being closed by the forward end of the valve when the latter is in position shown in Fig. 1 and being uncovered by the valve so as to be under control of the piston stem 5b when the valve is in the position shown in Fig. 2. A branch passage 15e leads to the forward face of thevf-orwa'rd flange 13b of the valve and still another branch 15t is arranged to be controlled by the said flange 13b. the latter closing branch 15f when in the position shown in Fig. 2 and opening it to exhaust through its groove 13C and passage 16 which communicates with the main piston controlled exhaust passage 17 which communicates directly with atmosphere. 'The' forward flange 13b of the valve further controls the admission and exhaust of motive .fluid to the rear face of piston-head 5a, mo-

tive fluid passing to the saine when the valve is in the forward. position (Fig. 1) around the central neck of the valve. through port 18, and connect-ing passage 18? which com-V municates with an annular groove 18b in the rearY end of the piston bore 4a. In the rearward position of the valve (Fig. 2) port 1SV communicates with forward groove 13c of the valve which connects in both positions of the valve with the auxiliary exhaust port 16. An exhaust passage 19 vents the rear face of the rearward flange 13b of the valve to permit movement of the valve tothe position shown in Fig. 2. i

The operation of the tool is briefly as follows Assuming the parts 'to be in the position shown in Fig. lvalve 13l has justshifted forwardly as a result of the pressure of the air trapped in the rearward end of bore 4b which was effective on the pressure surface of the valve provided by the rear edge thereof. The motive fluid passes from the live air chamber 14, around the central neck of the valve., 'through port 18 and passage 18a to the rear head of the piston driving` the lalter forwardly. As the piston stem 5" uncovers the ports 13il in the valve motive fluid at full pressure also becomes effective. against the end of stein 5b so that the piston advances with full pressure on both its forwardly act-ing pressure areas. The piston advances freely due to the unrestricted escape of air in the forward end of the bore 11" through the main exhaust passage. 1'? and, after the closing of the latter by the piston, through the auxiliary exhaust comprising port 15b, passage 15, branches 15 and 5f,

forward groove 13c of the valve and exhaust port 16. Vfhen the piston .reaches the position shown in Fig. 2 it uncovers the main exhaust passage 17 thus venting the rearward end of piston bore Ll. At about the same time'the piston stem 5b uncovers port 15 and admits motive fluid from the small bore t into passage 15n whence it extends in both directions, forwardly through port 15h to become effective against the front end of the piston head 5 to drive the piston rearwardly and rearwardly through passage 15C and branch 15e to become effective against the forward face of for 'ard flange 13" to shift the valve rearwardly to the position shown in Fig. 2. Thereupon forward flange 13" of the valve opens port 15d to bore 4t and closes port 18 to the motive fluid supply but opens` it to the auxiliaryexhaust through itsgroove 13C and xhaust port 16. The piston now moves rearwardly against the constant pressure of motive fluid on the end of its stem 5l. Shortly after beginning its rearward movement piston sten'i') closes port 15 but motive fluid still continues to pass to the front end of piston bore 4, through port 15l. branch 15, passage 15"L and port 15h, until 151 is in turn closed by the piston stem. The piston then moves rearwardly Lunder the expansion of the motive fluid in the forward end of bore 1L until the main exhaust .passage 17 is opened whereupon it continues to move rearwardly' under its acquired momentum. By the time the end of the piston stem vhas closed the air inlet ports 13L in the valve the pressure on the forward end and forward face of the forward flange 13b is suflicientlyA reduced to be overcome by the pressure on the rearward edge of the valve, whereupon the valve moves forwardly and the parts assume the position shown in F ig. 1 thus completing the cycle.

In case the piston 5 should be at rest in the position shown in Fig. 1 with the valve in its rearmost position (Fig. 2) a restrictedlive air port 20 is provided connecting the live air chamber 14; with passage 18a to permit suflicient mot-ive fluid to reach the rear end of the piston bore la to start. the

vpiston on its forward movement whereupon that the use of a reversible valve-of simple forni and design adds to the simplicity and cheapness of the tool, and that the arrangement whereby two of the pressure areas of the piston are piston controlled while only one is valvel controlled secures toV a considerable extent the positive action of the valveless tool with the added advantage of rel.- atively free movement of the piston resulting from the use of auxiliary valve controlled exhausts in addition to the main exhaust.

l claim as my invention:

1. ln a fluid pressure tool, a cylinder having a differential piston chaniber, a piston reciprocable therein providing two pressure areas for driving it in one direction and a single pressure area forreturning` it, portsr and passages controlled by `said piston for admitting motive fluid to two of said areas.y and a sleeve valve defining a portion of said piston chamber and moving in timed relation with said piston for controlling` the admission of motive fluid to the other pressure area of the piston.

2. In a fluid pressure tool, a cylinder having av differential piston chamber. a piston reciprocable therein, providing` two pressure areas for driving it in one direction and a single pressure area for returning ity ports and passages controlled by said piston for adn'iitting motive fluid to two of said areas5 a sleeve valve defining a portion of said pis-` ton chamber and movingin timed relation with said piston for controlling the admission of motive fluidY to the other pressure area of the piston, a main exhaust controlled by said piston for the portion of thc piston chamber adjacent two of said areasa and auxiliary exhaust means controlled by said valve for one of said last named areas.

3. ln a fluid pressure tool, a cylinder having a differential piston chamber, a piston reciprocable therein, providing two pressure areas for driving it in one direction and a single pressure area for returning it, ports and passages controlled by said piston for admitting motive fluid to two of said areas, a sleeve valve defining a portion of said piston chamber and moving in timed relation llo wit-'lr saidI piston for controlling' the admissioir of motive'r fluid tothe other presslu'e area' of the piston, -a mam exhaust vcontrolled'f hy said piston for the portion of Athe7 pistonv chamber adjacent two of said areas, and auxiliaryexhaust means controlled'by saidi valve rfor both-ofsaid last named areas.

4. I=n= a'E fluid pressure tool; a cylinder havingv a differential piston chamber, ka piston reoiprocable therein, providing twopressure sure area of the piston, a main` exhaust con-` trolled by said piston for the portion of' the piston chamber one of' which is the said valvecontrolled area, and auxiliary exhaust means controll-ed loy said valve t'or one of said last named areas. v n

5. In a fluid pressure tool, a cylinder having a differential piston chamber, a piston reciprocalole therein, providing two pressure areas for driving it in one direction and a single pressure area for returning it, ports and passages controlled by said piston for admitting motive fluid to two of said areas-l a sleeve valve defining a portion ot said piston chamber and moving` in timed relation with said piston for controlling the admission of motive fluid to the other pressure area of the piston. a main exhaust controlled by said piston for the portion ol the piston chamber adjacent two of said areas, one of which is the said valve controlled area, and auxiliary exhaustl means controlled by said valve for both of said last named areas.

6. In a fluid pressure tool, a cylinder providing a differential piston chamber, a differential piston reeiprocable therein comprising a head and a projecting stem of smaller diameter, a sleeve valve defining a portion of the piston chamber into which the stem of the `piston passes, said valve having ports controlled by said stem continuously in communication with the motive fluid supply, means controlled by said piston adjacent two of said areas,-

eontlrolled by said valve for controlling the admission of motive fluid to the rear face of the piston head said? val-ve having live air ports controlled hy the lpiston'sten'nA means controlled hy said piston sten'rforperiodically admitting motive fluid for a limited `period to the liront head to effect thel rearward vstroke oli the piston,

valve and said piston stem for admitting face of' the piston f and means controlled jointly by' said-y motive fluidtor a 'further yperiod to thefront face of the pistonhead. i f Y 7 8. In a fluid pressure tool, a cylinder providing a differential piston chamber, a differential piston vreeiprocahle therein comprising a head and a projecting stem of smaller diameter7` a sleeve valve defining a portionof the piston chamber into which the stem of the piston passes, -said valve hav ing live air ports controlled by said stem, means controlled hy said piston for admitting mo-l tive fluid to the other pressure' area of said head, a piston controlled main exhaust for thechamber on both sides 'of said piston head, and'auxiliary valve controlled exhaust means for one side of saidpiston head.

9. In a fluid pressure tool, a cylinder providin;` aA differential piston chamber, a differential piston reeiprocahle therein comprising` a head and a projecting stem of smaller diameter', a sleeve valve defining a portion of the piston chamber into which the stem of the piston passes,ports and pasy sages controlled by said valve for controlling the vadmission of motive fluid to the rear face of the piston head said valve having live air ports controlled by the piston stem, means controlled by said piston stem for periodically admitting motive fluid 'for a limited period to the front face' ofthe piston head Ato effect the rearward stroke of the piston, 'and means controlled jointly hy said valve l and said piston stem for admitting motive fluid .for a further period to the front face of the piston head, a piston controlled main exhaust for both faces of said piston head, and auxiliary valve controlled exhaust means for one face of said piston head.

10. Ina fluid pressure tool,` a cylinder having a differential piston chamber, a two diameter piston reciprocable therein having a head and a stem, a sleeve valve at one end of the piston chamber anddefining a part thereof' and moving in timed relation with said piston, said valve having ports there- 1 ULI llt) through under control. of the piston stem for admittingY motive' fluid against the end thereof,'means including a flange on said valve for controlling the admission of motive fluid against the rear -face of the piston head, means including a groove on said valve flange for providing an auxiliary exhaust for said last named pressure area of the piston, a piston controlled main exhaust, ane piston controlled means for supplying motive fluid to the forward ieee of the piston head. v

11.111' n fluid pressure lool., u eylirnfler having u diii'erenliial piston chamber, r. two diameer piston reeipi'oeuhie therein having u head und stern, u sleeve vulve al one end el1 the piston elmvniber und defining u purl; thereof -and moving; in timed relulion Wih Seid piston, Suid vulve having porle therethrough under Control oil the piston elem for admitting' motive fluid uguinel the end Vthereof7 u piston controlled eghuust 'for the end faces of the piston head, piston controlled. ineens for admitting motive fluid t0 the forward fuere of Jthe piston hearhmeuns including e flange on Suid vulve for controlling the udiniseion 'Oilf motive Huid tothe rear face of. said piston head, and auxiliary exhaust means for both faces 0l? Suid piston head ineluiling :i groove in the exterior 0i Suid vulve Hnge.

Signed by nie 2O day oi May 1925. I

' EDVARD V. STEVENS. l

ut Detroit, Mieliiguin this 

